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IP dropped packets

Hi,

Doing a "show IP traffic" to a Cisco 6K switch, I encountered a lot of "no route" and "encapsulation failed" IP dropped packets. (a little less than 10%)

I was wondering if someone knew what these 2 categories stood for ?

I mean, have you got an example of packet that would be put in that category ?

Thanks,

Romain PAGE

1 REPLY
Cisco Employee

Re: IP dropped packets

Hi Romain,

Encapsulation failed usually indicates that the router had no ARP request entry and therefore did not send the datagram. An example situation is when there is asymmetric routing and the ARP table and MAC address table is disjointed due to different aging times in these tables. You may see a number of incomplete entries in the output of "show ip arp"

No route is counted when the Cisco IOS software discards a datagram it did not know how to route.

A couple of examples when this can occur is if there is no route for a given subnet and there is no default route configured on the router, or the subnet in a packet that can't be routed due to its default gateway being down.

Documented here:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/ip_r/iprprt1/1rdip.htm#wp1020634

HTH,

Bobby

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